Serum Electrolyte disorders Flashcards
Potassium Normal Range
- 3.5-5.5 mEq/L
- 98% intracellular
- muscle cells
- Kidney imp for regulation
- Acidosis draws K out of cell / Alkalosis drives it into cell
K+ effect on cell membrane
- Inc K+
- sustained depolarization => weak animal
- inc excitability
- dec membrane potential
- Dec K+
- Sustained hyperpolarization => weak animal
- dec excitability
- inc membrane potential
Inc K+ effect on heart
Arrhythmias
- Increasing K+
- peaking of T wave =>
- Atrial standstill, widened QRS and T
- Depression of ST
- Biphase tracing
- Ventricular tracing
- Ventricular fibrillation
- Terminal
- Arrhythmias
- sinus bradycardia
- sinus arrest
- First deg AV block
- Nodal rhythm
- idioventricular rhythm
- ventricular tachycardia
- ventricular fibrillation
- ventricular arrest
Dec K+ effect on heart
Arrhythmias that can occur
- Dec K+
- Low T wave
- Atrioventricular conduction defect
- sagging ST
- Prominant U wave….WTF is this?
- Arrhythmias
- Ventricular premature beats
- Atrial tachycardia
- Nodal tachycardia
- Ventricular tachycardia
- Ventricular fibrillation
Clinical signs Hypokalemia
- Serum K+ < 2.5 mEq/L
- Muscle weakness is primary sign
- Other signs
- lethargy
- confusion
- PU/PD
- carb intolerance = low K causes inc in blood glucose, less insulin secretion…
- ileus
- EKG changes unpredictable
General causes of hypokalemia
- Movement into cells
- insulin
- GI loss
- vx/d
- Renal loss
- cats
Vomiting without diarrhea think….
- obstruction => always look under the tongue of every vomiting dog and cat for string of linear foreign body
- pancreatitis
Hypokalemia TX with K
- Mild (3.0-3.5 mEq/L)
- 20 mEq/L
- Moderate (2.5-3.0)
- 30-40 mEq/L
- Severe (< 2.5)
- 60 mEq/L
K+ Rate of infusion
- 0.5 mEq/kg of body weight per hour
- can go up to 1.5 mEq/kg with EKG monitoring
*rate is more important than total amount
Hyperkalemia values
- Mild (5-6.5)
- Moderate (6.5-8.0)
- Severe ( > 8)
Signs of hyperkalemia
- Muscle
- weakness due to depolarization
- Cardiac
- excitation and conduction abnormalities (when > 7-8 mEq/L)
Sequence of hyperkalemic EKG changes
- High T wave (should only be 1/4 the R wave)
- Prolonged PR interval, high T wave, depressed ST segment
- Auricular standstill, Intraventricular block
- Ventricular fibrillation
*no P waves = atrial standstill
*oliguric/anuric animals, Addisonian criseses, K overdose, cats with urethral obstruction
Main mechanisms hyperkalemia
- Too much intake
- impaired excretion
- ARF
- Addison’s
- Shifting
- metabolic acidosis
- Drugs
- aldosterone inhibitors
- spironolactone
- ace inhibitors (angiotensin converting enzyme inhibitor)
- aldosterone inhibitors
Aldosterone
- acts on distal tubules of kidney
- Na reabsorption
- K secretion
*No aldosterone: K goes up, Na goes down
Other causes of Hyperkalemia
- Cell death
- Acidemia
- Lack of insulin
- Hypertonic plasma
- Medications
- B-blockers
- digoxin
- penicillin
- KCl IV fluid
- Severe exercise (rhabdomyelysis)
- stored blood (old red blood cell transfusion)
False Hyperkalemia
- Cushing’s dog with high platelet count
- normally take blood and put in clot tube (red tube, standard for chems)
- serum would be sent to lab, this serum would have lots of K released during the clotting process
-
THEN collect blood into a green tube (heparinized)
- This sample is plasma and will have true potassium measurement
- normally take blood and put in clot tube (red tube, standard for chems)
Treatment for hyperkalmemia
- Ca Gluconate
- won’t lower serum potassium but will save heart
- works within a few minutes
- NaHCO3
- lowers serum K (pushes K into cell)
- > 30 minutes
- not really used, needs high dose and side effects of bicarb
-
Insulin - dextrose
- lowers serum K (pushes K into cell)
- Diuresis - furosemide
- Hemodialysis
- Terbutaline, albuterol, aminophylline
- beta agonist => pushes K into cell
- minutes
Measurement of Na reflects
- Extracellular water content
Hyponatermia
Causes
- Big problems when Na+ < 120
- Brain swelling - demyelination
Causes
- Water gain-more common
- Na loss - Addison’s
Hyponatremia signs
- weakness
- apathy
- dementia
- stupor/coma
- absence of thirst
- decreased skin elasticity
- hypotension
- hypothermia
- shock
- seizures
- myoclonus
Hyponatremia Classification
- Euosmolar
- Hyperosmolar
- Hypoosmolar
2 main causes of acute hyponatremia
- Intake of large quantities of hypotonic fluid (oral/IV)
- Impaired H2O secretion
- inappropriate ADH release
D5W
Dextrose 5% in water
Not used to correct hypovolemia
hypernatremia
Na intolerant patients
TX Acute hypo Na
TX Chronic hypo Na
TX Acute hypo Na (occured w/in 24-36 hours)
- Remove causative factors
- Can correct rapidly over 24 hours
- Replace sodium at rate of at least 1 mEq/L/hr
TX Chronic hypo Na (occured over several days)
- Correct slowly
Hypernatremia
- Problems around 170 mEq/L => hypertonic encephalopathy
Hypernatremia main causes
- Na gain - uncommon
- water loss - common
Effects of Hyperosmolality on Neurons
- Hypertonicity
- Intracellular water => ECF
- Neuron dehydrates
- Retraction and tearing of meningeal vessels
- CNS hemorrhage
- Neuron dysfunction
- patient can die
Idiogenic osmoles
- In hypernatremia brain creates these to keep fluid in the brain
- If patient corrected too quickly the brain will swell
Hyper Na signs
- Fever
- Nausea
- Vomiting
- Seizures
- Coma
- Neuro signs
- Hypotension
- Tachycardia
- Oliguria unless DI
Types of hyper Na
- Hypovolemic: renal, GI
- Hypervolemic: hypertonic saline TX
- Euvolemic: DI
TX Hyper Na
- Stop water diuresis by giving ADH to DI patient
- Stop any hypertonic fluid infusion
- Give 0.45% NaCl or D-5-W IV
- Acute hyper Na can be treated over several hours, restored w/in 24 hours
- Chronic hyper Na correctly slowly over 48-72 hours
Alkolosis usually goes along with ______
- Hypokalemia
- causes insulin resistance
- LRS BAD
- lactate converted to bicarb in liver
- If rehydrating a sick patient but Na is rising too fast
- give Furosemide
Emergency medicine priorities
- Hypovolemia
- once BP is 60 it’s permissible, can give furosemide
- Acid-base
- Electrolytes
Central Pontine Myelinosis
- Iatrogenic brain demyelination from too rapid correction hypo Na
- Maximal rate of correction
- Don’t exceet 0.5 mEq/L/hr
- Max 8-12 mEq/L per 24 hours
